Ice-making machines that cool a brine solution to form an ice-brine slurry are known in the art. For example, U.S. Pat. No. 4,796,441 to Goldstein, assigned to the assignee of the present application, discloses an ice-making machine having a chamber with a fluid inlet to receive a brine solution from which ice is to be made and a fluid outlet to permit the egress of an ice-brine slurry from the chamber. The interior surface of the chamber defines a heat exchange surface. A tubular jacket surrounds the chamber. A refrigerant inlet and a refrigerant outlet communicate with the space between the jacket and chamber and are positioned at opposite ends of the ice-making machine. Refrigerant flowing through the space between the inlet to the outlet boils and in so doing, cools the brine solution in contact with the heat exchange surface. Refrigerant leaving the ice-making machine via the outlet is condensed and compressed before being fed back to the refrigerant inlet. A blade assembly is mounted on a rotatable shaft extending through the center of the chamber and is in contact with the heat exchange surface. A motor rotates the shaft so that the blade assembly removes a cooled layer of brine solution in contact with the heat exchange surface and directs the removed cooled layer into a body of brine solution within the chamber. The shaft is rotated at a rate such that the interval between successive passes of the blade assembly over the heat exchange surface inhibits the formation of ice crystals on the heat exchange surface.
U.S. Pat. Nos. 5,884,501 and 6,056,046 to Goldstein disclose an ice-making machine including a housing having a brine solution inlet to receive brine solution from which ice is to be made and an ice-brine slurry outlet to permit the egress of an ice-brine slurry from the housing. A heat exchanger within the housing has a heat exchange surface, a refrigerant inlet, a refrigerant outlet and at least one refrigerant circuit interconnecting the refrigerant inlet and the refrigerant outlet. Refrigerant flows through the at least one refrigerant circuit between the refrigerant inlet and the refrigerant outlet to extract heat from the brine solution contacting the heat exchange surface. A blade assembly within the housing carries a plurality of blades, each of which is in contact with the heat exchange surface. The blade assembly is mounted on a shaft, which is rotated by a motor at a rate such that the blades move across the heat exchange surface and remove cooled fluid therefrom thereby to inhibit the deposition of ice crystals on the heat exchange surface.
U.S. Pat. No. 6,305,189 to Menin discloses an installation for the continuous crystallization of liquids by freezing to form a bubble slurry with crystal nuclei, gas bubbles and concentrated unfrozen liquid. The installation includes a pumpless refrigeration circuit with a compressor, a water condenser, a cooling tower, an indirect refrigerated evaporator, an expansion valve, a low pressure receiver and a refrigeration accessories for volumetric crystallization of liquid flowing through the refrigerated evaporator. The installation performs preliminary liquid cooling at a predetermined temperature, adding gas into the cooled liquid and their intermixing, delivering mixed liquid and gas through the refrigerated evaporator and winding round the mixed liquid and gas into the refrigerated evaporator. Plastic wipers in the tube of the refrigerated evaporator move a cooled layer of the liquid mixed with gas bubbles (LMGB) in a spiral path towards the central longitudinal axis of the tube.
In order to maintain efficiency in ice-making machines of the above-described type, it is desired to inhibit the formation of ice on the heat exchange surfaces. As a result, in such ice-making machines the wipers or blades are typically moved over the heat exchange surfaces at a rate selected to avoid ice layer formation. Despite doing this, during the course of operation, ice crystals sometimes form on the heat exchange surfaces leading to the formation of ice layers on the heat exchange surfaces. When such an ice layer forms on the heat exchange surface, the ice layer acts as an insulator and reduces the efficiency of the ice-making machine. At this point it is often necessary to stop operation of the ice-making machine until the ice layer on the heat exchange surface melts. If the ice layer achieves any substantial thickness, the time required for the ice layer to melt can be significant. As will be appreciated, it is desired to determine when ice crystals begin forming on the heat exchange surface so that immediate steps can be taken to inhibit an ice layer from forming on the heat exchange surface.
It is therefore an object of the present invention to provide a novel sensor assembly for detecting ice crystal formation on a heat exchange surface and an ice-making machine incorporating the same. It is also an object of the present invention to provide a novel ice-making process.